I feel it's almost more likely for things to feel like they were cut rather than added. I wouldn't really be surprised if things like the super bosses end up cut and held back as DLC depending on the direction they take the game. I think a lot of the new stuff will be tweaks involving the scale of things being made more realistic to make the game more realistic and a lot of silliness getting changed or cut due to everything likely being fully voiced (such as the weird beginner's hall stuff).

It's been so long since I've played through the game though that I can't really think of many ways content would be added outside of possible Compilation stuff.